Step-by-step explanation:
Arithmetic mean formula is
A=(x1+x2+x3+....+xn)/n
in this case
A=(8+10+10+10+6+7+8)/7=
=59/7=
=8.42857143~=8.4
Answer:
10
they each go by ten
5-(1+5)= -1
-2(1+4)=-10
-3+15i
Apply complex arithmetic rule:
-3 * 3 -3 (-2) = -3